Semiconductor substrate processing is typically performed by subjecting a substrate to a plurality of sequential processes to create devices, conductors and insulators on the substrate. Semiconductor manufacturing processes are generally performed in a processing chamber configured to perform a single step of the production process. In order to efficiently complete a sequence of processing steps, a number of processing chambers is typically coupled to a central transfer chamber that houses one centrally located robot to facilitate transfer of the substrate between the processing chambers. A semiconductor processing platform having this configuration is generally known as a cluster tool, examples of which are the family of CENTURA® and ENDURA® processing platforms available from Applied Materials, Inc. of Santa Clara, Calif.
Generally, a cluster tool consists of a central transfer chamber having one or more robots disposed therein. The transfer chamber is typically surrounded by one or more processing chambers, and at least one load-lock chamber. The processing chambers are generally utilized to process the substrate, for example, performing various processing steps such as etching, physical, vapor deposition, chemical vapor deposition, and the like. Processed and unprocessed substrates are housed in substrate storage cassettes, also known as FOUPs, disposed in a factory interface coupled to the load-lock chamber.
The load-lock chamber is isolated from the factory interface and the transfer chamber by slit valves. Substrates enter the transfer chamber from the substrate storage cassettes one at a time through the load-lock. The substrate is first positioned in the load-lock after the substrate is removed from the cassette. The load-lock is then sealed and pumped down to match the operating pressure of the substrate transfer chamber. The slit valve between the load-lock and transfer chamber is then opened, allowing the substrate transfer robots to access the substrates disposed in the load-lock. In this fashion, substrates may be transferred into and out of the transfer chamber without having to repeatedly re-establish transfer chamber vacuum levels after each substrate passes through the load-lock or processing chambers.